1) Field of the Invention
The present invention relates to a digital audio signal processing apparatus.
2) Description of the Related Art
It has heretofore been known a digital audio signal processing apparatus which can provide a sound field control and tone control, which is disclosed in, for example, Japanese Patent Laid-Open No. 72615/1989. Such a digital audio signal processing apparatus is provided with a DSP (Digital Signal Processor) of a type wherein an audio signal issued from an audio signal source such as a tuner, etc. is subjected to digital processing to provide a sound filed control and tone control. The DSP includes not only an arithmetic operation means for performing arithmetic operation processing such as four rules of arithmetics but also a data memory for storing therein audio signal data to be supplied to the arithmetic operation means and a coefficient memory for storing therein coefficient data multiplied by signal data stored in the data memory. In addition, the DSP is so constructed that a delay memory for delaying the signal data can externally be provided. Furthermore, the DSP is also provided with a delay-time memory for storing therein delay-time data representative of the time required to take from writing of the signal data into the delay memory to reading of the same therefrom. In the DSP, the data transfer is performed between memories in accordance with a processing program or the data is transferred to the arithmetic operation means from the memory and therefore the arithmetic operation of the signal data is repeatedly carried out at a high speed. For example, input signal data is applied to the delay memory for producing delayed signal data. The delayed signal data is transferred to the arithmetic operation means through the data memory in order to be multiplied by the coefficient data, whereby reflected sound data in which attenuation in level is taken into consideration is obtained, thus making it possible to define an acoustic space. It has also been practiced to form a graphic equalizer by the arithmetic operation processing for thereby subjecting signal data to tone control.
In addition, new data and processing programs are fed from a microcomputer provided on the outside of the DSP each time the control mode is changed by a prescribed operation, so that the data and the processing programs in the DSP are rewritten, thus enabling various arithmetic operation processing.
However, in such a digital audio signal data processing apparatus, since the number of per-unit bits of data or programs, which can be transmitted by the microcomputer, is normally smaller than that of data controlled by the DSP, the rate of transferring the coefficient data or programs from the microcomputer to the memory is slow. A relatively long time was thus required to rewrite the data or programs. For example, even in the case of use of the same graphic equalizers of such a type that arithmetic operation processing which defines a graphic equalizer of two-channel common type comprising a plurality of bands is changed to arithmetic operation processing which defines a graphic equalizer of separated two-channel type ccmprising a plurality of bands in accordance with a mode change-over, a relatively long time was necessary for rewriting of the programs.
In addition, since the data or programs must be stored in the memory for each mode on the side of the microcomputer with a view toward causing the DSP to carry out various arithmetic operation processing in the operation mode, the prior art is accompanied by the problem in that the memory is required to have a large capacity.